1. Field of the Invention
The invention is related to the field of magnetic storage devices, and in particular, to methods for manufacturing sliders using a lapping process.
2. Statement of the Problem
Many computer systems use disk drives for mass storage of information. Disk drives typically include one or more sliders or heads that write to and read from a storage media. To read data from the storage media, the storage media spins and generates a magnetic field. The magnetic field in the presence of a sensor in the slider, such as a Giant Magneto-Resistive (GMR) sensor, modulates the resistance of the sensor. The change in resistance of the sensor is detected by passing a sense current through the sensor and then measuring the change in voltage across the sensor. The resulting signal is used to recover the data encoded on the storage media. To write data to the storage media, an inductive element in the slider produces a magnetic field that records the data on the storage media.
Sliders are typically manufactured on a substrate wafer that includes an array of sliders. The sliders are arranged in rows on the wafer with kerfs between the sliders connecting the sliders in the row. The most commonly used material used to fabricate a wafer is an aluminum oxide—titanium carbide compound (Al2O3—TiC) (referred to herein as Alumina Titanium Carbide or AlTiC). An AlTiC wafer is first cut into quadrants with a mechanical saw. For each quadrant, a rough lapping process is performed on an air bearing surface (ABS) side of a row of sliders in the quadrant. The rough lapping process removes many microns of material on the air bearing surface of the sliders to a desired rough lapping depth. Typically, the quadrants are parted into separate rows or individual sliders before they are lapped to the final target forms using finer lapping plates. If the final lapping is done in the row form, the row of sliders can be partially cut between the sliders in the kerfs from the air bearing surface side of the row to allow for flexing of the row during the rough lapping process. The row is then final lapped and parted to individual sliders. If the final lapping is done on individual sliders, a final lapping process is performed on the individual sliders to create a target sensor height of the sensor in each individual slider. The target sensor height provides a desired magnetic characteristic for the sensor in each individual slider and it may be reflected by the resistance of the sensor. The final lapping process also creates the base plane on which the air bearing pattern will be created in following processes to allow the slider to fly at desired height above a storage media.
Another material used to fabricate a wafer is silicon. Sliders made from silicon have some advantages over sliders made from AlTiC. First, silicon sliders tend to have a lower mass and may cause less damage to the storage media if the slider contacts the storage media. Also, using silicon to fabricate the sliders allows for building integrated circuits into the sliders using well-known semiconductor technologies.
One challenge in manufacturing sliders out of silicon is that silicon is more brittle than AlTiC and may chip or crack if cut using a mechanical saw. Thus, a Deep Reactive Ion Etching (DRIE) process is used to part the wafer into individual sliders. Parting refers to cutting or otherwise separating the wafer. The DRIE process may part the entire wafer into individual sliders. One problem with parting the entire wafer into individual sliders using the DRIE process is that performing a rough lapping process on individual sliders is not efficient. There is about 20 μm of material that needs to be removed from the air bearing surface of the individual sliders. Removing 20 μm of material on an individual slider basis may create the additional problem of the air bearing surface of the slider not being perpendicular to the deposit end of the slider.
The DRIE process may also part the wafer into rows of sliders. For an individual row of sliders, a rough lapping process is performed on an air bearing surface side of the row of sliders. The DRIE process is then used to part the row into individual sliders. One problem with parting rows of sliders in this manner is that every row needs to be parted using the DRIE process again, which can be costly. The rows may also be parted into individual sliders by re-aligning the rows into an array and using the DRIE process on the array to part the individual sliders. One problem with parting rows of sliders in this manner is that it involves an additional process and may not be precise. Additionally, the DRIE process involves chemicals which may be dangerous to sensors, especially after the sensors are exposed after the rough lapping process.